Jacking systems for use in the construction of buildings



Attorney 5 Sheets-Sheet 1 J. W. JANSZ Fig.1

JACKING SYSTEMS FOR USE IN THE CONSTRUCTION OF BUILDINGS H CH0 Inventord. W Ja nsz Wm w m 1 /w 9 fl O oooooh oMvooo 40.] A||\|/O o Q m M m m I4 mm I m 0 0 Z 1 W J W F 0 I w m m 0 o :I 1% t? m 1. O O0 000 OO 0 2 o mll 4 MMN i w Aug. 13, 1968 Filed March 28, 1966 3, 1968 J. W. JANSZ I3,396,944

JACKING SYSTEMS FOR USE IN THE CONSTRUCTION OF BUILDINGS Filed March 28,1966 5 Sheets-Sheet 2 E 12 E12 Fig.3

29 NV 29 W m [32 1H J T 30 T 35 l W 52 Inventor JNJansz A Home y 3, 1968J. w. JANS-z 3,396,944

JACKING SYSTEMS FOR USE] IN THE CONSTRUCTION OF BUILDINGS Filed March28, 1966 Y 5 SheetsSheet 5 W 1T1'\ 3o r- --rmm1m-, 3 351 3 8 l I s s a;g l 52 54 i I 59 I EEE Z 5'5 l I w 62 G3 64 65 ea 67 61 49 Inventor JIM.Jmsz By :M

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JACKING SYSTEMS FOR USE IN THE CONSTRUCTION OF BUILDINGS Filed March 28.1966 5 Sheets-Sheet 4 y7/// //(cy Inventor 16M Attorney 7 J. W. JANSZAug. 13; 1968;

JACKING SYSTEMS FOR USE IN THE CONSTRUCTION OF BUILDINGS y 2 m .1 r5LID. e 0 I. e m A h e2 S J m m N o h 6 S H J 5 B 9 .U

Filed March 28, 1966 United States Patent 3,396,944 JACKING SYSTEMS FORUSE IN THE CONSTRUCTION OF BUILDINGS Joost Werner Jansz, The Hague,Netherlands, assiguor to Richard Costain Limited, London, England, aBritish company Continuation-impart of application Ser. No. 454,367,'May 10, 1965. This application Mar. 28, 1966, Ser. No. 537,975 Claimspriority, application Netherlands, May 8, 1964, 6405158; Great Britain,Mar. 31, 1965, 13,738/65 11 Claims. (Cl. 25489) ABSTRACT OF THEDISCLOSURE The present invention relates to a jacking system for use inthe construction of buildings in which the vertical and horizontalstructures of each successive storey, starting from the top storeydownwards, are constructed at or near ground level and subsequentlyraised by a plurality of jacking devices (together with all thecompleted storeys thereabove) to permit the construction of the verticaland horizontal structures of a further storey therebeneath. The jackingsystem includes horizontal level control means for maintaining thefloors at all times in a near-perfect horizontal plane during thejacking operation. This is achieved by controlling the jacking devicesso that when a jacking device rises through only a small predeterminedsubstep of the order of /2 mm. it is stopped from rising further untilall the jacking devices have been raised through the predetermined smallsubstep.

The present invention relates to the construction of buildings,particularly to high buildings of ten or more storeys, although theinvention is applicable to the construction of buildings of lesserheight.

The present invention is a continuation-in-part of my application Ser.No. 454,367, filed May 10, 1965, which is assigned to the same assigneeas the present application and has now issued under Patent No.3,309,062.

A method of constructing tall buildings is known (see our prior BritishPatent No. 956,134) in which the vertical and horizontal structures ofeach successive storey, starting from the top storey downwards, areconstructed at or near ground level, and subsequently raised by onestorey height (together with all the completed storeys thereabove) topermit the construction of a further storey therebeneath. By this methodthe necessity for tall cranes and high hoists is avoided and thebuilding workers only have to work at low heights.

The raising of the successive storeys is effected by jacking devices onwhich the full weight of the building rests until the building hasreached its full height, when the jacks are removed and the buildinganchored to its foundations.

In the prior practical application of this method, as described in theaforesaid patent specification, the building is supported on a centralcore from which all the floors are supported in cantilever fashion. Thejacking devices act directly on the central core structure which,together with the projecting floors, provides a substantially rigidstructure.

In applying the method to buildings of which the floors are not rigidand capable of being raised as an integral unit, the difficulty arisesof raising all parts of the floor by substantially equal amounts so thatall parts of the floor will at all times be in a near-perfect horizontalplane and the introduction of excessive stresses in the structure, dueto differential deflections, which can give rise tocracking or otherdamage to the structure, will be avoided.

The present invention has for its object to provide a "ice method of andapparatus for raising a building structure by means of jacking deviceswhich overcomes the above diificulty.

To this end the invention consists in raising the building by means of aplurality of jacking devices which are auto matically controlled sothat, at each actuation, each jacking device can rise by only a smallpredetermined substep, preferably of the order of /2 mm, such raisingmovements of the jacking devices being registered in a control devicewhich prevents the jacking devices from again being actuated to executeanother substep until the control device registers that all the jackingdevices have correctly completed the previous substep.

In order that the invention may be more clearly understood, theapplication thereof will now be particularly described by way of examplein connection with a building comprising a central core structure fromwhich the floors project and of which the perimeters of the floors aresupported by columns, reference being made to the accompanying drawings,in which:

FIGURE 1 is a diagrammatic plan view of the building.

FIGURE 2 is a diagrammatic vertical section of the building, duringerection.

FIGURE 3 is a hydraulic circuit of the jacking system and details of oneform of jack construction.

FIGURE 4 is a schematic diagram of the electric control circuit of thejacking system.

FIGURE 5 is a modification of the hydraulic circuit of FIGURE 3.

FIGURE 6 is a view explaining the construction of the wall of thecentral core structure.

FIGURES 7, 8, 9 and 10 are diagrams explaining alternative methods oferecting the supporting columns.

FIGURE 11 shows in more detail a side view of the apparatus for carryingout the method illustrated in FIG: URE 10.

FIGURE 12 is an end view of FIGURE 11.

FIGURE 13 is a plan view on the line A--A of FIG- URE 11.

Referring to FIGURES 1 and 2, the building generally comprises a centralcore structure comprising a supporting wall 101 around which the floors102 project, their perimeters being supported on supporting columns 103.The floors can also project inside the central core walls which may alsoaccommodate the staircase, lifts and other services.

The method of construction consists in first constructing, at or nearground elvel, a base slab 104 beneath which is a jacking chamber 105 ofwhich the base is carried on very strong foundations 106. The slab 104may be supported from the base of the jacking chamber by perm-anent ortemporary piers 107. Disposed in the jacking chamber are a plurality ofjacking devices 1 located at positions for raising the core wall 101 andthe supporting columns 103, the slab being provided with openings 108,109 through which the wall structure and supporting columns canrespectively pass as they are raised by the jacking devices.

The roof structure 110 is first constructed on the slab 104 and liftedby the jacking devices in steps to the full height of the storey belowit, during which a section of the supporting wall strupcture 101 andcolumn sections 103 therebeneath are constructed or erected andsupported from the jacking devices or temporary supports as will behereinafter explained. The next floor structure is constructed on theslab 104 either before, after or during the erection of the wallstructure and column sections which have to support it, and is thenraised in steps by the jacking devices with the already erectedstructure there-above, the operation being repeated for each floor untilthe Whole building is erected. The jacking devices are operated in amanner such that the floors will be raised, with the central core andsupporting columns, so as to be at all times in a near-perfecthorizontal plane whereby to avoid the introduction of excessive stressesin the structure due to differential deflections which could causecracking or other damage to the floor structures and the joints betweenthe fioors and the central core or supporting columns. To achieve thisthe jacks are 'so constructed and so automatically controlled that, ateach actuation, each jack can rise through only a predetermined smalldistance or substep, for example /2 mm., all the jacks having tocomplete this small substep before any of the jacks can again beactuated to raise the structure through a similar small substep.

One form of construction of stroke-controlled jack suitable for use incarrying out the method of this invention, and the mode of controllingthe jacks for achieving the level control of the structure will bedescribed with reference to FIGURES 3 and 4. FIGURE 3 shows thehydraulic circuit for the jacks, two groups I and II of which are shownat the top of the figure, the left-hand jack of group I being sectionedto show the construction of the jacks, the remaining jacks only beingshown in outline. FIGURE 4 shows the electrical circuit of the jackingsystem and includes a fragmentary plan, on an enlarged scale, of theratchet teeth on the jack and the associated electric switches.

Dealing first with the construction of the hydraulic jack 1 itself,this, as shown, comprises a cylinder 2 in which slides a piston 3secured to a piston rod 4. The jack 1 is of the single-acting type,liquid under pressure for lifting the load being supplied to one side 5of the piston 3 through pipes 7, 8 from a pump 23 driven by a motor 24.

The piston rod 4 is provided with a screw thread on which is threaded anut 9. The nut 9 is movable by auxiliary mechanism which controls thejack stroke, consisting of ratchet teeth 10 (see also FIG. 4) providedaround the nut 9 and cooperating with a pawl 11, which is actuated by anauxiliary single-acting hydraulic cylinder 12 provided with a piston 13.To rotate the nut 9 by means of pawl 11 and ratchet teeth 10, liquidunder pressure from pump 23 is supplied to the side 14 of the piston 13through pipes 7 and 15. A common solenoidoperated control valve 26provides for simultaneous supply of pressure liquid from pump 23 throughpipes 7 and 8 to the jack cylinder 2, and through pipes 7 and 15 to theauxiliary cylinder 12 of the jacks of each group. Each control valve 26is actuated by a solenoid 29, and when in its right-hand position (asshown in FIGURE 3) connects oil pressure from pump 23 and pipe 25 topipe 7 and hence to pipes 8 and 15. When the solenoid 29 is energised,the valve 26 is moved to its left-hand position where the supply of oilfrom the pump to the pipe 7 is cut OE, and the pipe 7 is connected viathe passage 30 in the valve 26 to the pipe 32 leading back to the oilreservoir 31. Upon release of the oil pressure in the cylinder 12, thepawl 11 and piston 13 are returned to their initial positions by acompression spring 19 which may, for example, be incorporated in thecylinder 12. The jack cylinder 2 is connected via a nonreturn valve 21with the pipe 7 so that, upon release of the pressure in pipe 7, thepressure in the jack cylinder 2 will be maintained. A manually operatedvalve 27 is provided for releasing the oil pressure from the jackcylinder 2 when the jack is to be individually lowered for the insertionof a spacer block or the like to start another jacking step. Forlowering a jack a worm wheel may be provided on a zone of the peripheryof the nut 9 whereby the nut 9 may be turned backwards, for example bymeans of a worm fixed in a hand drilling machine or the like, to allowthe piston rod 4 to move downwards.

The nut 9 effects a follow-up movement during the jack stroke,continuously applying itself against the jack cylinder 2 so that the nutalso serves as a locking device which safeguards the jack againstuntimely lowering in the event of failure of the hydraulic pressure.

The pitch of the screw thread on the piston rod 4 and the number ofratchet teeth 10 around the nut 9 are so related that each advance ofthe nut by a distance of one ratchet tooth corresponds to the jackpiston being raised through a height of /2 mm. Associated with theratchet teeth 10 is a switch 20 which produces a signal each time itmoves over a tooth to actuate the solenoid 29 of its associated valve 26which moves to cut off the supply of oil to the jack or jack groupconcerned and at the same time to connect the pipe 7 to the pipe 32.Associated with the pawl 11 are two switches 17, 18, the switch 18actuating each time the pawl commences a forward movement and each timeit completes a return movement. The switch 17 is a safety switch whichis only actuated by the pawl 11 if the latter moves through a distancecorresponding to more than one tooth of the ratchet 10 (preferablycorresponding to a distance of two teeth), thus indicating improperoperation of the jack stroke control mechanism and stopping furtheractuation of the entire system as will be hereinafter described.

The jack is provided with a further safety switch 22 which cooperateswith the nut 9 and actuates in the event that the nut for some reason,fails to remain in contact with the jack cylinder 2 which can only occurif the nut has not been able to follow up sufiiciently quickly tocontrol the rise in the piston. Preferably the switch 22 is arranged tooperate if the nut 9 separates from the jack cylinder by a distance of 1mm.

The hydraulic circuit also includes a solenoid operated bypass controlvalve 28 which is switched to its left-hand position by the solenoid 33when all the valves 26 are in their left-hand positions and cutting offthe supply of oil to the jacks, so that the oil from the pump 23 is thenbypassed through the passage 35 in the valve 28 and pipe 36 back to theoil reservoir 31. 34 is a high-pressure relief valve which normallyregulates the maximum oil pressure which can be applied to the jacks butcan also be moved to an open position to leave a free passagetherethrough. The system also includes a low-pressure relief valve 37since it is sometimes necessary, for example when raising a jack afterit has been lowered, to apply to the jack a lower working pressure, thecorresponding control valve 26 then being selectively actuated to feedoil to the jack in question. In this case, the operation of theappropriate manual control to open the selected valve 26 also closes thebypass valve 28 and locks the high pressure relief valve 34 in its openposition leaving a free passage to the low-pressure relief valve 34 sothat the oil pressure applied to the jack cannot exceed the preset valueof the low-pressure relief valve 37. Oil filter 38 cleans the oil whichflows through the relief valves.

The multiplicity of jacks required to raise the entire buildingstructure is generally divided into groups each consisting of two .ormore jacks supervised by a master jack equipped with a master contact20. The other jacks in a group are hydraulically interconnected as shownin FIGURE 3 and act as slave jacks. The safety contacts 17 act as limitcontacts for both slave and master jacks. If the master contact 20 of amaster jack fails to work, the system will be automatically stopped bycontact 17. If a slave jack in a group runs faster than the master jackfor some reason or another its contact 17 operates the control valves26, 28, thus stopping the system. While FIGURE 3 shows an arrangement inwhich the pump 23 is common to several groups .of jacks, it will beunderstood that each jacking group could have its own individual pumpingunit.

Electrically the system is built up in series fashion so that afollowing /2 mm. substep can only be initiated when all the contacts 18,which are connected in series, have delivered their signals, firstindicating that all the pistons 13 have actually started a forwardstroke and secondly indicating that they have all properly retracted.All the master contacts 20 must also have indicated that the nuts havemoved by one tooth before a subsequent substep can be initiated. When acontact 17 or 22 actuates, this specific group stops immediately whilethe other groups finish their substep normally. It is then impossible tostart the next substep automatically and the fault has to be rectifiedbefore further raising substeps can be performed.

FIGURE 4 diagrammatically shows the electric circuit of the system. Onejack group and pumping unit are shown. From the contacts 17, 18, 20 and22 on a jack 1 wires lead to a connection box 45 on the pumping unitindicated by the block 46 in which are indicated the valves 26 and 28,the pump motor 24, and a relay 47 for selecting whether the pumping unitoperates under high pressure or low pressure. The equipment in thepumping unit 46 is connected by wires to its corresponding connectionbox 48 on the central control desk 49 which includes the memory controlunit 50 and a plurality of sets of indicator lamps 51 corresponding tothe contacts 17, 18, 20, 22 of each hydraulic group. In the memorydevice 50 of the response of the contacts is registered and the seriescontrol effect is supervised. 52, 53 and 54 are three counters,respectively the substep counter, the block height counter and the totalcounter. The mains supply is indicated at 55, the starters beingindicated at 60 With their fuses at 61. Associated with the unit 50 arevarious switches, namely the start-stop switch 62, group-separatingswitch 63 which serves to cut out one or more hydraulic groups for anumber of substeps if required, selector switch 64 for selecting high orlow pressure operation, switch 65 by means of which one or more contacts22 can be cut out of operation, deblocking switch 66 for deblocking acontact 17 which has been actuated, and deblocking switch 67 fordeblocking a contact 22 which has been actuated.

So long as the pulses from contacts 20 and 18 are received in the unit50 from each jacking group at each substep, and no pulses are receivedfrom contacts 17 or 22, the memory unit will reset at the completion ofeach substep and the substeps will automatically repeat so long as thestart-stop switch 62 is operated. The structure is therefore raised withthe floors always in a near-perfect horizontal plane. In the event of afault occurring as indicated by improper operation of a contact 18 or20, or by operation of a contact 17 or 22, the jacking system stopsoperating. At no time during jacking can one part of a floor he raisedabove another part of the floor by more than 1 mm., nor fail to beraised as high as another part of the floor by more than 1 mm., withoutthe Whole jacking system coming to a halt. Therefore, by ensuring thatall floors are raised with great precision in the horizontal plane, theintroduction of parasitic stresses in the structure is avoided duringjacking operations.

FIGURE shows a modification of the hydraulic circuit of FIGURE 3 whichcan improve the smooth working of the system. Only those parts of thecircuit are shown which are necessary for understanding thismodification. The pipes 8 and 15 are not connected together as in FIG-URE 3 but are connected to the pipe 7 through individual devices.Between the pipe 7 and the pipe 15 is a reducing valve 39 capable ofbeing preset to a desired pressure value. Valve 39 is shunted by anonreturn valve 40 which permits oil flow to bypass the valve 39 whenoil pressure is released when the control valve 26 moves to its lefthandposition. The manual valves 27 connect with the pipe 15. Between thepipe 7 and the pipe 8 is a springloaded nonreturn valve 41 which opensto allow oil pressure to be applied to the jack cylinders. The operationis as follows. When the control valve 26 is in its right-hand positionas shown, the oil flow is initially-resisted by the spring-loading onvalve 41 but passes through the reducing valve 39 to apply pressure tothe cylinder 12. The valve 41 opens and oil pressure is applied to thejack cylinder, but the pressure applied to the nut-actuating cylinder 12does not at any time exceed the pressure set by the reducing valve,irrespective of the value of the pressure applied to raise the jackwhich depends on the load to be raised and thus increases as thebuilding work proceeds.

When the valve 26 moves to its left-hand position, the

oil pressure in the cylinder 12 is released and .oil flows back to theoil reservoir through the pipe 15, nonreturn valve 40, passage 30 andpipe 32. When a jack is to be lowered and its manual valve 27 is opened,oil flows back to the reservoir through the same path. The nonreturnvalves 21 and 41 both stop oil flow in the same direction and providedouble security against leakage of oil from the jack cylinders.

' FIGURE 6 illustrates a method of constructing the supporting walls 101which, in the embodiment shown, is constructed of blocks 111 which maybe made of concrete, steel or other suitable material and which may bebonded together to form the bearing walls or sections of the bearingwalls by means of in situ reinforced or prestressed concrete jambs orlintels, and/or in situ reinforced or prestressed in-filling or casing,and/or horizontal posttensioning.

As shown, the blocks 111 are raised simultaneously in substeps by allthe jacks 1 as above described, and when raised through thepredetermined jacking step, equivalent to the height of a block, asindicated by the substep counter 52 at the controldesk, each jack islowered in turn to allow the insertion of another block, such as 111a,the jack then-being raised under reduced pressure until it takesthe-load through the inserted block. This reduced pressure on the jackallows the inserted block to be moved into correct relation with theother blocks in the same horizontal row, for example by a sidewaysforce. When all the blocks of a horizontal row have been inserted, andpreferably bonded together, for example by horizontal post-tensioning,the whole wall structure can then again be raised in substeps throughthe height of a row of blocks, the raising of the blocks simultaneouslyraising the floor structures thereabove which are joined to the bearingwall.

Instead of using the blocks as a permanent part of the wall structure,they may simply serve as spacers and after the structure has been raisedthrough a desired height, for example the height of a storey, thespacers may be removed and replaced by either in situ construction orprefabricated bearing wall sections. During this operation the load oneach jacking device is either transferred selectively to adjacentjacking devices or to some form of temporary support. During raising thespacers may be temporarily held together, for example by horizontalposttensioning.

The permanent bearing walls may increase in thickness, width or numberfrom top to bottom of the building in accordance with the loads theyhave to carry.

FIGURES 7 to 10 are diagrams explaining various methods of erectingsupporting columns. In the various figures successive stages of theerection are indicated by the references (a) to (c) or (a) to (d).

As shown in FIGURE 7 the columns 103 are raised by jacks 1 positioneddirectly therebeneath (as shown at stage a) and after each column hasbeen raised in substeps through a jacking step, which may correspond tothe stroke of the jacks or some selected lesser distance, each column issupported (as shown at stage 12) on temporary supports comprising a yoke112 and temporary support members 113, the columns having brackets 114which rest on the yoke. The jack is then lowered to allow the insertionof a spacer block 115 and the raising operation is repeated untilsuflicient spacer blocks have been inserted corresponding to the heightof a column section 103. Then (as shown at stage 0), while thepreviously erected part of the column is supported on the yoke 112 andtemporary supports 113 at that level, the spacer blocks 115 are removedand replaced by a column section 103. The temporary support memberspreferably support the load from the base of the jacking chamber and mayalso comprise spacer blocks.

In the modification shown in FIGURE 8, the column is raised in similarsteps by successively inserting spacer blocks 115 while the column issupported on temporary supports, but in this case each column isprovided with a plurality of brackets 114 so that the yoke 112 canalways be supported by temporary support members 113 at the same height,either above the base slab 104 (as shown) or therebeneath. In FIGURE 8,stages (a) (b) and correspond to stages (a) (b) and (c) in FIGURE 7.

In the modification shown in FIGURE 9, the columns are raised by jackingdevices comprising pairs of jacks 1 acting respectively on opposite endsof yoke member 112 which supports the column (as shown at stage a). Atstage b the column is supported by a temporary support member 113 (e.g.,spacer blocks) disposed directly beneath the columns, while the jacksare retracted to allow the insertion of spacer blocks 115 between thejacks and the ends of the yoke 112. When a column has been raisedthrough the required height, a further column section 103 is insertedtherebeneath (see stage 0) and is supported on a temporary support 113(see stage d) while the yoke is separated from the column section withwhich it was engaged and is engaged with the newly inserted columnsection before repeating the raising operation.

FIGURE shows a further modification in which a column is again raised byjacking devices comprising a pair of jacks 1 and a yoke 112, but insteadof inserting spacer blocks between the jacks and the yoke ends, thespacers are constituted by spacer members 116 secured to the columnsection 103 above the yoke. After a column has been raised by the jacks(see stage a) it is supported by a temporary support 113 (see stage b)while the jacks and yoke are lowered and further spacer members 116 aresecured to the column. The spacer members 116 conveniently comprisemetal plates applied to opposite sides of a column and bolted together.The upper edges of the plates bear against the bottom edges of theplates thereabove. The upper edges of the upper pair of plates 116 on acolumn section bear against a head plate 117 on the column section,which head plate is secured to and bears against a foot plate 118 at thefoot of the column section 103 thereabove. After a column section has'been raised through the height of a column section, another columnsection is inserted therebeneath (see stage 0) and is supported by atemporary support 113 (see stage d) while the jacks and yoke are loweredto engage the yoke beneath the head plate 117 of the newly insertedcolurrm section 103.

FIGURES 11 to 13 show respectively a side view, end view and a plan of apractical construction of the yoke and spacer plates for carrying outthe column lifting method described with reference to FIGURE 10'.

Referring to FIGURES 11 to 13, the yoke comprises two side beams 112,112a which are adapted to be urged together and clamped against oppositesides of the supporting column 103, shown as an H-section steel column,by means of the handwheels 119 coacting with screw bars 120 extendingbetween the side beams of the yoke. Opposite ends of the yoke beams reston the plungers of the pair of jacks 1. By loosening the handwheels 119the yoke beams can be released and moved down the column, when the jacksare lowered, while the column is being supported on a temporary support.The spacer plates 116 are bolted together across opposite faces of thecolumn by bolts 121 so that the upper and lower edges of adjacent platesabut each other to support the load, the upper edge of the upper platebearing against the underside of the head plate 117 of a column sectionwhich is secured to the foot plate 118 of the column section thereaboveby bolts 122. After a pair of spacer plates 116 have been fixed, and thejacks are raised with low pressure so that the yoke beams bear againstthe bottom edges of the spacer plates, the handwheels 119 are tightenedto clamp the yoke beams to the column section.

The floor structures may be constructed of steel, concrete or acombination of these or any other suitable material, and may be whollyor partly prefabricated or constructed in situ. They may be prestressedeither by pre-tensioning or post-tensioning.

The jacking devices may comprise individual hydraulic or screw jacks, orcombinations of two or more such jacks with a yoke or other bridgingstructure. The tem porary supports which take the load oil the jackingdevices while the jacking device is being retracted prior to carryingout another jacking step may comprise adjacent jacking devices,specially provided screw or hydraulic jacks, blocks and shims of variousheights or adjustable wedges, blocks and short stroke screw or hydraulicjacks, yokes or bridging structures supported on pedestals or blocks, orother convenient supports. The spacers used may comprise blocks, plates,beams or column pieces and may be made of concrete, steel or othersuitable material.

Column sections may be prefabricated or made in situ and may be ofsteel, concrete or other suitable material. The column sections areconveniently of storey or halfstorey height.

While particular embodiments have been described, it will be understoodthat various modifications may be made without departing from the scopeof the invention, and that the method according to this invenion ofraising the structure so that the floors remain in a near-perfecthorizontal plane during jacking, may be applied to building structuresin which the floors are suported partly on columns and partly on walls,or wholly on columns or walls, the walls being either core, perimter ortransverse walls or combinations of these. Further, instead ofconstructing the floor structures at ground level, they may beconstructed at the level of one of the lower floors of the building.

I claim:

1. A jacking system for use in the construction of buildings in whichthe vertical and horizontal structures of each successive storey,starting from the top storey downwards, are constructed near groundlevel and subsequently raised by a plurality of jacking devices,together with all the completed storeys thereabove, to permit theconstruction of the vertical and horizontal structures of a furtherstorey therebeneath, said system including a plurality of jackingdevices, at least one source of power for actuating said jackingdevices, screw means associated with the jacking devices, drive meansrotating said screw means through an angle corresponding to the amountby which its associated jacking device rises, switch means producing asignal each time said screw means turns through a small anglecorresponding to the jack being raised through a predetermined smallsubstep, means responsive to a Signal from a jacking device to stop theassociated jacking device from actuating, a control device in which thesignals from all the jacking devices are registered, and means forpreventing subsequent actuation of a jacking device to execute asubsequent substep unless the control device registers Signals,corresponding to the same previous substep, from all the jackingdevices.

2. A jacking system as claimed in claim 1, wherein each jacking devicehas associated therewith means for producing at least one further signalin the event of improper operation of the jacking device by over-runningthe predetermined substep, and means responsive to the production of anysaid further signal for preventing the jacking devices of the systemfrom executing a subsequent substep.

3. A jacking system as claimed in claim 1, wherein each jacking deviceincludes a hydraulic jack having a piston movable in a cylinder, thepiston having a piston rod provided with a screw thread, a nut rotatablymounted on said screw thread and having ratchet teeth, a pawl associatedwith said ratchet teeth and driven by an auxiliary hydraulic device toturn the nut in a direction to screw down the piston rod and bearagainst a part which is fixed relative to the jack cylinder, pipes forsupplying hydraulic fluid to said jack cylinder and auxiliary hydraulicdevice from a source of hydraulic fluid under pressure whereby said pawlturns the nut to perform a follow-up movement when the jack piston israised by applying thereto hydraulic fluid under pressure, a controlvalve for interrupting the supply of hydraulic fluid to said pipes, anelectric switch cooperating with said pawl and ratchet mechanism toproduce a signal when said ratchet has turned by an amount correspondingto a substep, means actuated by said signal to operate the control valveto stop the supply of hydraulic fluid to the jack and releasinghydraulic pressure from said auxiliary hydraulic device, means returningsaid pawl upon said release of hydraulic pressure from said auxiliaryhydraulic device, and means feeding said signal to the control device tobe registered thereby.

4. A jacking system as claimed in claim 3, wherein said signal isproduced by a switch actuated by the ratchet teeth and wherein a secondelectric switch is associated with the pawl and is actuated thereby toproduce a signal at the beginning of a pawl stroke and at the end of thereturn stroke of the pawl, means feeding the signals produced by saidsecond switch to the control device, means insaid control device forregistering the signals received from the second switches associatedwith the respective jacking devices of the system, and means responsiveto the means for registering the signals from said second switches forpreventing the jacking system from executing a further substep unlessthe control device registers signals indicating that each pawl hasstarted a stroke and has completed its return stroke.

5. A jacking system as claimed in claim 4, wherein each jacking deviceincludes a third switch associated with its pawl and arranged to operateonly if the pawl executes a movement exceeding that corresponding to thepredetermined substep, and means responsive to the operation of any ofthe third switches associated with the respective jacking devices forpreventing the system from executing a subsequent substep.

6. A jacking system as claimed in claim 5, wherein each jacking deviceincludes a fourth switch arranged to operate if the nut separates fromthe fixed part against which it bears on follow-up by a distance of theorder of twice a substep, and means responsive to the operation of anyof the fourth switches associated with the respective jacking devicesfor preventing the system from executing a subsequent substep.

7. A jacking system as claimed in claim 3, including a pressure reducingvalve in the pipe leading to the auxiliary hydraulic device, whereby theauxiliary hydraulic device always operates at the hydraulic pressure setby the reducing valve irrespective of the hydraulic pressure necessaryto raise the jacking devices, and a non-return valve shunts the pressurereducing valve to allow free flow of hydraulic fluid from the auxiliaryhydraulic device when the fluid pressure therein is released.

8. A jacking system as claimed in claim 3, wherein a jacking devicecomprises two jack cylinders arranged side-by-side and spaced apart andwith their pistons projecting upwardly and bridged by a yoke comprisingtwo beams between which can be located a column section to be raised,means being provided for forcing said beams together to clamp on to acolumn section therebetween.

9. A jacking system as claimed in claim 3, including means for loweringa jacking device after it has been raised through a desired number ofsubsteps without lowering other jacking devices, and means for reducingthe hydraulic pressure applied to said jacking device to raise it afterit has been lowered.

10. A jacking system as claimed in claim 3, in the construction of abuilding of which the floors are supported at least in part onsupporting columns, including temporary support means for temporarilysupporting a raised column in its raised posit-ion while the associatedjacking device is lowered preparatory to another jacking step.

11. A jacking system as claimed in claim 8, including spacer platesadapted to be secured to a column above the yoke to be raised thereby,temporary support means being provided for supporting the column at itsraised height while the yoke is lowered to enable spacer plates to besecured to the column preparatory to another jacking step.

References Cited UNITED STATES PATENTS 2,975,560 3/1961 Leonard 254893,036,816 5/1962 Stubbs et a1. 254- X 3,201,088 8/1965 Long 254-893,327,997 6/1967 Zenke 254-89 OTHELL M. SIMPSON, Primary Examiner.

